Matlab loop to assign rows to cell array

Question

I have a big cell array A=cell(a,b,c,d) and a row vector B with dimensions 1-by-b.

I want to build a loop in MATLAB that does the following:

for i=1:n
   B = Calculate_row(input1,input2) %this is a function that creates my B row
   A{a,:,c,i} =  B(:)
end

anyway if I try to do A{a,:,c} = B(:) I receive the following error:

Expected one output from a curly brace or dot indexing expression, but there were b results.

And if I try to do A(a,:,c) = B(:) I receive the following error:

Conversion to cell from double is not possible.

Is there a way to do this? (I know a less elegant way that probably works would be to assign each value to the cell separately, but I would prefer not to do it).

You probably just want this A(a,:,c) = {B(:)}. However, the way you call Calculate_row (if that is indeed how you are calling it) is really bad practice. Never call a script from another script, make sure you only call functions. Adapt Calculate_row to be a function that might look something like B = Calculate_row(input1, input2,...) — Dan
– Dan, Commented May 5, 2016 at 8:13
Did you miss out something? You assign it in a loop but you are not using i as an index somewhere in the assignment - furthermore A has 4 dimensions, but you are only giving 3 dimensions in the assignment. Did you want to do this A{a,:,c,i} = B(:)? (just guessing). Please give a value for the 4th dimension and try the assignment again :-) — tim
– tim, Commented May 5, 2016 at 8:14
Also have a look here: de.mathworks.com/help/matlab/matlab_prog/… -> Depending on your data you might not even need Cells, I don't know. But if not required, then rather don't use it as it makes things much more complex :-) — tim
– tim, Commented May 5, 2016 at 8:24
Also pretty nicely explained here: stackoverflow.com/a/9055336/701049 :-) — tim
– tim, Commented May 5, 2016 at 8:25

Community · Accepted Answer · 2017-05-23 12:07:53Z

1

One way to do this is to make B a cell array and then take advantage of comma-separated-lists:

B_cell = num2cell(B);
[A{a,:,c}] = B_cell{:}    %// or [A{a,:,c,i}] = B_cell{:} if tim's comment is correct

Have a look at Loren Shure's article Deal or No Deal and also this answer for more.

The problem with your syntax, A{a,:,c} = B(:), is that the RHS (i.e. B(:)) is just one single matrix whereas the LHS is a comma-separated-list of b results. So you are basically requesting that 1 output be assigned to b variables and MATLAB doesn't like that, also hence the error message.

The problem with A(a,:,c) = B(:) is that indexing a cell array with () returns a cell array and you can't just assign a matrix (i.e. B(:)) to a cell array hence you second error.

edited May 23, 2017 at 12:07

CommunityBot

11 silver badge

answered May 5, 2016 at 8:20

Dan

45.8k20 gold badges98 silver badges170 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Patapunfate Over a year ago

Thank you Dan, I did as you suggested me but this way I still receive an error. When I type [A({1,:,1,1}] = B_Cell{:} I receive the error [A({1,:,1,1}] = B_Cell{:} ↑ Error: Unexpected MATLAB operator. With the arrow pointing at the" : ".

Patapunfate Over a year ago

Oh god I did not see it, my apologies, now it works. Thank you

Collectives™ on Stack Overflow

Matlab loop to assign rows to cell array

1 Answer 1

2 Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

2 Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related